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Taming the Enemy
Published in Norman Begg, The Remarkable Story of Vaccines, 2023
For some vaccines, it’s a particularly challenging balancing act. The bacteria that cause some types of meningitis are covered in a thick mucus-like coat called a polysaccharide. This polysaccharide coat is the bit that determines their ability to make you ill, so it needs to be in the vaccine; however, our immune system doesn’t mount such a strong response to a polysaccharide as it does to other parts of the bacteria, which are made of protein. To get a round this, the polysaccharide is linked to a different protein, which helps it to stimulate the immune system, thus improving the immune response. These hybrid vaccines that contain polysaccharide joined to a protein are known as conjugates. Vaccines for meningococcal meningitis, pneumococcal disease (which causes pneumonia and blood poisoning), and Haemophilus influenzae type B (“Hib”, another cause of meningitis) have been made using conjugate technologically. I have a personal research interest in this class of vaccines and conducted trials of several vaccines that ultimately ended up being used to vaccinate children against meningococcal meningitis and Hib, including one vaccine that combined both into one vaccine.
Immunomodulatory Therapies
Published in David E. Thurston, Ilona Pysz, Chemistry and Pharmacology of Anticancer Drugs, 2021
According to the World Health Organization (WHO), there are currently four types of vaccines available: (1) Live attenuated vaccines prepared from a weakened (attenuated) form of the living infectious organism which can create a strong, long-lasting immune response, (2) inactivated vaccines prepared from the killed (e.g., by heat or chemicals) infectious organism which provide a weaker immune response requiring additional booster shots, (3) subunit vaccines consisting of just the antigenic component of the organism produced by recombinant techniques and also providing a weaker immune response, and (4) toxoid vaccines that contain a deactivated version of the toxin produced by the disease-causing organism (e.g., diphtheria and tetanus toxins). However, many other types of vaccines are recognized such as conjugate vaccines and DNA vaccines. Adjuvants are often added to vaccine formulations to stimulate antibody production against the antigen. They can accelerate, enhance, and prolong the immune response to the vaccine antigens, and aluminium salts are the oldest and most common adjuvants in clinical use today.
Adaptive humoral immunity and immunoprophylaxis
Published in Gabriel Virella, Medical Immunology, 2019
Conjugate vaccines. As previously mentioned, most polysaccharide vaccines have shown poor immunogenicity, particularly in infants. This lack of effectiveness is a consequence of the fact that polysaccharides induce mostly T-independent responses with little immunological memory. This problem appears to be eliminated if the polysaccharide is conjugated to an immunogenic protein, very much like a hapten-carrier conjugate. Hib conjugate vaccine. The first conjugate vaccines to be developed involved the polyribosyl-ribitol-phosphate (PRP) of Haemophilus influenzae type b (Hib). Four conjugate vaccines are available, based on Hib-polysaccharide conjugated to different protein carriers, such as diphtheria toxoid (PRP-D), a diphtheria toxoid-like protein (PRP-HbOC), tetanus toxoid (PRP-T), or meningococcal outer membrane protein (PRP-OMP). All are equally efficient, but to secure the carrier effect, critical for the boosting effect of repeated immunizations, the same vaccine should be used for the primary immunization and boosters.
Invasive meningococcal disease epidemiology and vaccination strategies in four Southern European countries: a review of the available data
Published in Expert Review of Vaccines, 2023
Irini Zografaki, Marios Detsis, Maria Del Amo, Raffaella Iantomasi, Ana Maia, Eva Agostina Montuori, Cristina Mendez
Besides their use in serogroup classification, capsule polysaccharides of N. meningitidis [1] were also the first targets for vaccines developed for this microbe. Polysaccharide vaccines against serogroups A and C were the first efficacious meningococcal vaccines, developed in the 1960s, later on licensed as quadrivalent (A, C, Y, and W) vaccines as well, which were however poorly immunogenic in infants [12]. This limitation was subsequently addressed by the introduction of polysaccharide-protein conjugate vaccines [12], which were also superior than polysaccharide vaccines in terms of conferring immunologic memory [13] and resulted in herd effects from immunization of adolescents [14,15]. Conjugate vaccines have become widespread in the developed world since the late 1990s and are also available as monovalent (A or C) and as quadrivalent (A, C, W, and Y) vaccines [12].
Trends and health burden of hospitalized acute respiratory infections and impact of Haemophilus influenza immunization in a Tunisian university hospital: a twelve-year study
Published in Libyan Journal of Medicine, 2020
Manel Ben Fredj, Wafa Dhouib, Meriem Kacem, Cyrine Bennasrallah, Ons Mehrez, Hela Abroug, Imen Zemni, Aicha Gardabou, Koubaa Jamel, Slaheddine Chouchene, Naceur Rouatbi, Asma Belguith Sriha
However, there is no conclusive evidence of differences in the immune response to monovalent or combined Hib conjugate vaccines. In fact, a review about the successes and the contribution of hexavalent combination Hib vaccines in Europe from 2000 to 2014; showed a higher acceptance. On the other hand, there are some concerns that this combined form may reduce Hib immunogenicity [38]. Our results may be related to the high Hib vaccine coverage among children born since 2011. This high coverage vaccine provided by combined vaccines is explained by the reduction of injections number for babies and the reduction of visits to health-care centres. In addition, the effect of Hib Conjugate Vaccine on the prevention of pneumonia in hospitalized infants for bronchiolitis was shown by a case-control study [39]. In NVC, male children dominated Hib pneumonia admissions whereas no sex-difference was notified in VC, this result was concordant with conclusions in literature [40].
A primary care physician’s approach to a child with meningitis
Published in Southern African Journal of Infectious Diseases, 2018
I Govender, C Steyn, G Maricowitz, CC Clark, MC Tjale
Visitors to Saudi Arabia arriving for the purpose of Hajj/Umrah or for seasonal work are required to submit a certificate of vaccination with the quadrivalent (ACYW135) vaccine against meningitis, proving the vaccine was administered no less than 10 days before arrival. The conjugate vaccine is the valid option, when available, and confers a protection of at least five years. The vaccine should have been administered not more than five years prior to entry into the country. The conjugate vaccine is licensed for persons between nine months and 55 years old. The responsible authorities in the visitor’s country of origin should ensure that adults and children aged two years and above are given at least one dose of the quadrivalent vaccine and state the name of the vaccine used clearly on the vaccination card.24